PREFACE TO THE 2ND EDITION Although this dictionary is concerned primarily with the terminology of contemporary aerospace technology@ words that are used in other scientific fields@ such as computing@ astronomy@ and geophysics@ have also been included. This dictionary should thus prove useful to students and teachers of aerospace engineering@ scientists@ technologists@ and technicians in research and industry. In such a fast-moving technology as aerospace engineering@ new terms are created and others become redundant almost weekly. We have made every effort to give more space to the emerging technologies and to delete the more obsolete terms. While this dictionary contains over 20@000 terms and definitions@ size alone is a poor criterion of merit. A work of reference must stand or fall by its accuracy and authority. The authority and accuracy of this work rests on the decades of experience of SAE engineers who created the SAE standards and the generous contributions from the National Aeronautics and Space Administration (NASA).